Tuesday, December 05, 2006


Organic chicken is less nutritious, contains more fat and tastes worse than free range or battery-farmed meat, scientists have discovered. Tests on supermarket chicken breasts found organic varieties contained fewer omega-3 fatty acids and lower levels of antioxidants, giving the meat an inferior taste. Some were found to contain twice as much cholesterol.

The study, by food scientists at Strathclyde University, contradicts the common view that the premium paid for organic meat guarantees a healthier and tastier product. Despite costing twice as much, the organic products scored lower in all the nutritional tests in the study, "It is safe to say that you are not getting any nutritional benefit from buying organic chicken," said Alistair Paterson, co-author of the study, which is published in the International Journal of Food Sciences and Nutrition. "You could be better off buying conventional or free-range chicken. There is no guarantee that organic chicken gives you more omega-3, better taste or a lower cholesterol level."

Organic food, which is produced according to standards covering the use of pesticides, additives, animal welfare and sustainability, has become big business with sales in the UK doubling in six years. Last year, the market was worth 1.6 billion pounds, up from 800 million in 2000, according to Datamonitor, the market research firm, and is forecast to be worth 2.7 billion by 2010. However, there are growing concerns that the increasing industrialisation of organic farming to meet demand has led to a dilution of its green credentials and quality.

The Strathclyde team found that organic chicken was lower in antioxidants than conventional or free range chicken and, in blind tastings, scored lowest for succulence. According to Paterson, the differences in taste and nutritional composition are due to the feed the animals are given. Synthetic vitamin supplements are standard in conventional feed but are prohibited under organic farming rules.

The Soil Association, representing organic producers, insisted that organic standards were not being compromised. "This research contradicts the bulk of evidence which shows organic food is higher in omega-3, vitamins and minerals than conventional chicken," said Hugh Raven, director of Soil Association Scotland.



They are at last admitting that the "hockey stick" picture of temperature stability before the 20th century is wrong -- but only because they think they can find an explanation for one of the earlier cold periods that does not upset their theories too much. The most honest sentence in the article is however the last one -- which I have highlighted in red.

The Gulf Stream - the ocean current that helps to bring warm weather to much of the North Atlantic region - was significantly weakened during the period known to historians as the Little Ice Age, new research reveals. The discovery supports the notion that a slowing of ocean currents - as some fear might happen in our future - can have significant consequences for climate.

From around 1200 until 1850, during which average temperatures across the Northern Hemisphere dipped by around 1 oC, the strength of the Gulf Stream also slackened by up to 10%, oceanographers report. The Gulf Stream, which is part of a vast pattern of currents nicknamed the ocean conveyor belt, carries warm surface waters from the tropical Atlantic northeastwards towards Europe. The reduced flow that occurred during medieval times would have transported less heat, contributing to the icy conditions that persisted until Victorian times.

"This gives us some sense of the natural range in strength. If the change is greater in the future then maybe that will mean something unusual is happening," says David Lund of the California Institute of Technology in Pasadena, who led the research while based at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution.

Weakened waters

A weakening Gulf Stream has been predicted to have dire consequences for temperate climates in the Northern Hemisphere. But oceanographers say that it is very unlikely to shut down, as depicted in the Hollywood blockbuster The Day After Tomorrow. "That's definitely an absurdity," Lund says.

But the new research by Lund's group shows what can happen if the Gulf Stream is weakened. He and his colleagues studied the remains of tiny animals called foraminifera in sediments off the coast of Florida, where currents feed into the Gulf Stream. Changes in the composition of oxygen isotopes in their shells reflect changes in water temperature and salinity, which in turn reveals the density of the water they were living in.

Mapping the water density between Florida and the Bahamas gives the researchers a picture of how fast the current was moving between them. Lund and his team report their results, which extend back some 1,000 years, in this week's Nature1.

Fresh or salty

Lund and his colleagues think that the Gulf Stream's weakening was caused by a southward shift of the zone of tropical rains that usually feed fresh water into the Atlantic Ocean off the coast of Florida. This rain provides a less-dense top layer of water that bolsters the surface current flowing north. Their measurements show that, during times when the current was weakest, the waters were saltier, suggesting that they contained less fresh water from rain.

The slowing of the current this way can fix itself, however - the extra saltiness of the water should help the water to sink at the northern end of its cycle, Lund says, driving the bottom half of the ocean circulation and re-energizing the current.

This process is in contrast to current fears about the Gulf Stream. Climatologists are worried that continued melting of the Greenland ice sheet could dump too much fresh water into the northern end of the circulation system, where cold waters normally sink and drive the bottom half of the current - dense waters flowing south along the ocean floor. Too much fresh water in the north makes the water less dense and less likely to sink, slowing the current.

Some fear that this process would not fix itself, but rather lead to a runaway effect that slows the current even more severely. Researchers measuring the ocean currents today say that the Gulf Stream shows no clear signs of slowing. Last month, a scientific meeting on the issue resulted in media reports that the Gulf Stream had shut down completely for 10 days in 2004. But as Harry Bryden of the University of Southampton, who led that study, explains, the temporary shutdown actually occurred in deeper currents that form just part of the complex circulation system. The Gulf Stream, he says, was unaffected. "The Gulf Stream seems rather robust to us," he adds.

But big changes could lie in our future. "Now, with the amount of carbon dioxide in the atmosphere, we're in a 'no analogue' situation," Lund says. With the world warming and the poles melting, it's impossible to say what might happen to the currents.

"We just don't know."


The relevant journal abstract follows:

Gulf Stream density structure and transport during the past millennium

By David C. Lund et al

The Gulf Stream transports approximately 31 Sv (1 Sv = 10^6 m^3 s^-1) of water 1, 2 and 1.3 10^15 W of heat 3 into the North Atlantic ocean. The possibility of abrupt changes in Gulf Stream heat transport is one of the key uncertainties in predictions of climate change for the coming centuries. Given the limited length of the instrumental record, our knowledge of Gulf Stream behaviour on long timescales must rely heavily on information from geologic archives. Here we use foraminifera from a suite of high-resolution sediment cores in the Florida Straits to show that the cross-current density gradient and vertical current shear of the Gulf Stream were systematically lower during the Little Ice Age (ad 1200 to 1850). We also estimate that Little Ice Age volume transport was ten per cent weaker than today's. The timing of reduced flow is consistent with temperature minima in several palaeoclimate records4, 5, 6, 7, 8, 9, implying that diminished oceanic heat transport may have contributed to Little Ice Age cooling in the North Atlantic. The interval of low flow also coincides with anomalously high Gulf Stream surface salinity10, suggesting a tight linkage between the Atlantic Ocean circulation and hydrologic cycle during the past millennium.


No comments: